1. Field of the Invention
This invention relates to a synchronous electric machine having a rotor in which the field poles are supported by a lamination ring (chain) which is guided tangentially and shrunk onto a hub arranged on the rotor shaft in such a manner that the lamination ring is lifted only at speeds above the nominal speed of revolution.
2. Description of the Prior Art
A synchronous machine of the above type is described in U.S. Pat. No. 3,128,403.
In hydro-electric generators having large diameters, a hollow shaft is frequently used as the rotor shaft and the turbine shaft is coupled to it. The hub of the rotor itself may also be designed as a hollow rotor shaft. In such designs, the hollow rotor shaft is subjected to higher stresses at the point of coupling to the turbine shaft than on the other side of the machine, as the stresses due to centrifugal force, the weight of the rotor, and shrinkage forces of the lamination ring (chain) are added to the existing stresses resulting from the transmission of torque and, possibly, of water thrust and the weight of the turbine. It therefore becomes important to make the design of the rotor such that the allowable stress level in the material of the shaft is not exceeded at this critical point.